The thing I am often surprised more boat handlers don't seem to realize is how slowly (relatively speaking) things happen in a boat, and the heavier the boat the slower they happen. We, and I'm sure most people on this forum, see boaters frantically hauling back and forth on their throttles and shifters as they over-react to everything they see the boat doing.
Perhaps we were lucky in that we learned a lot of what we know about larger boat maneuvering from the 25 ton, 60' steel narrowboats we've run in the UK starting in 1990, but we quickly found that applying a little power, a little rudder, a little opposite thrust, and then waiting to see what happens results in a far more controlled and calm maneuver than trying to counter every little boat motion.
While I am not always able to do this, my self-imposed goal when docking our boat is to shift each transmission no more than twice from when we approach our slip or a dock in gear to when we are stopped in or alongside it. The key, we have found, is learning our boat's reaction to inertia, both when applying power and taking it off, and how the boat reacts to the direction the props, or a prop, is turning and the angle of the rudders.
While wind or current can sometimes conspire to defeat meeting my two-shifts-only objective, usually even they do not speed things up so much as to warrant the seesawing of throttles and shifters we so often observe on other boats.
It takes a lot to get a 30,000 pound boat moving and it takes a lot to get a 30,000 boat stopped. Knowing how much it takes in each case as well as being able to judge where inertia is going to make the boat end up is the key to an easy, smooth maneuver in my opinion.